Photographic camera with exposure meter photocell adjustable for discrete scanning



Jan. 29, 1963 H. MELLE 3,075,440

PHOTOGRAPHIC CAMERA WITH EXPOSURE METER PHOTOCELL R DISCRETE SCANNINGADJUSTABLE F0 Original Filed Oct. 16, 1956 5 Sheets-Sheet 1 FIG. I.

INVENTOR HEINZ MELLE ATTORNEYS.

D w I l l l lllrllllllln r i P .1 LC

Jan. 29, 1963 LE 3 5,440

H. MEL ,07 PHOTOGRAPHIC CAMERA WITH EXPOSURE METER PHOTOCELL ADJUSTABLEFOR DISCRETE SCANNING Original Filed Oct. 16, 1956 3 Sheets-Sheet 2 FIG.5. FIG. 6.

a7 4 as HI IIHI IHHHII H IIIHI INVENTOR HEINZ MELLE WM fl ATTORNEYS.

Jan. 29, 1963 H. MELLE 3,075,440

PHOTOGRAPHIC CAMERA WITH EXPOSURE METER PHOTOCELL ADJUSTABLE FORDISCRETE SCANNING Original Filed Oct. 16, 1956 5 Sheets-Sheet 3INVENTOR.

Heinz Mel Ie ATTORNEYS United States Patent 6) This invention relates tophotographic cameras provided with exposure meters and, moreparticularly,'to

cameras of this type in which certain disadvantages of a thearrangements hitherto used are reduced oreliminated. The'pre'sentapplication is a division of my c'opending application SerialNob-16,247, filed October 16, 1956, now Patent No. 3,007,381, issuedNovember 7, 1961.

"Cameras embodying the present invention are preferably provided withbuilt-in exposure meters, and it is' fundamentally immaterial what typeof exposure meter is used, so that either optical or photo-electricmeters are use-able. However, as photo-electric exposure meters arebeing evermore widely'used in practice, due to the objectivity of theirlight measurements, they are 'preerred-to optical'expo'sure meters.Accordingly, in the following description, the primary emphasis will beplaced on arrangements in which the light measurement is eftfected bymeans of a photo-electric cell having an ele trical indicatinginstrument connected to its'output.

Exposure meters integrate the various luminous flux densities of thefield of the object, and thus indicate an average value of illumination.However, knowledge of such average value often is not sutficient forsuccessful exposure of the negative material. As a result, manuracturers of exposure meters have suggested to users thereof the application ofcorrective factors based on empirical observationsfthe particularfactors suggested for each case being in accordance with the conditionsprevailing in such case. It Willbe appreciated that such expedient-s arenot a satisfactory'solution'of the problem ofobtaining correct exposurevalues, and thus'are not capable of obviating defective exposures.

Ir'rthe usual use of conventional exposure meters, theilluminationfmeasured by the exposure meter is not the same as that.acting on the photo-sensitive film through the objective of the cameraThere" a'reseveral reasons for this, which areexpla'ined in more detailbelow.

The electric current outputs of photocells, as'a result of andcor-responding'to light incident on the'cells, are

very small, so that, particularly with lower light intensities, thepointer deflections of: the measuring instrument are notexactlydefinedwand are not clearly readable. To avoid this difficulty, it hasbeen proposed to usephotocells haying relatively large light exposedsurfaceabut rangem ns f; this. ype findpnly limited use where theexposure meters are built-ininto'cameras as, inview of dimensionallimitations of the cameras, only a small free space is available for.mounting of a photoeell. As a r esult, resort, has bel'enhad' to anexpedient wherein the light inoidentupon thefphotocell was made [to beincident over a relatively large solid angle thereon. Thus, photographiccameras have been provided, wherein 'the solidangle of the lightincidenton the electric exposure meter is even larger than the solidangular field of the camera objective. i

The use of such wide angle exposure meters results in larger currentoutputs from tliephoto'cells' with consequently greater pointerdeflections for a'given intensity of incidentlight. However, with sucharrangement it is possible, or even. probable, that the indicated lightintensity does not correspond to the actual value of light intensityavailable 'for exposure of the film. Thus, if the exposure value settingof the camera is based upon the light value as measured by the exposuremeter, a defective exposure m ay r'esult, even in those cases in whichthe aforementioned empirical corrective 'factors have been taken intoconsideration. The reason for this'is that such factors are based merelyon probability calculations and are correctly understood by layman onlyinfrequently, i

Such measurements of the light values by exposure meters are basicallywrong because the light values measured thereby are detern linedon thebasis of acetic of light rays which is ditierent from that incident uponthe filrn to be exposed. If the solid angle of the light incident on thephotocellis'equal to that incident through the objective on the film orother negative material, improved results are obtained. However, evenundersuch conditions, defective exposures can result, as will beapparent from general co 'isiderations' of geometric optics.

The present invention is directed to exposure meter arrangements whereinthe aforementioned disadvantages cell are coordinated in accordance withthe principlesiof the invention;

FIG. 4 is a somewhat diagrammatic elevational view illustrating oneembodirnenft of' a photo-electric cell mounting arrangement inaccordance with the inventi'on;" i

FIGS. 5 and 6 are, respectively, a somewhat diagrammatic sectional viewand a somewhat diagrammatic elevational view illustrating a furthermodification of the invention; i

FIG. 7 is a view, similar to FIG. 4, illustrating still anotherembodimentof the invention; and l FTG. Sis a'per'spective view, partlybroken away, of a preferred embodimentof theinve'ntionQ "Referring tothe drawings, FIGS. 1 and 2 illustrate how a defective measurement ofthe available lightvalues can 'actuallyimpair an exposure. 'Withintheobject field of the carneralobjective, which is indicated'as limited by.the frame r a bunch of flowers is placed on top of a table which has arelatively low'illumination. The illumination on the flowers is at arelatively low level due to the flowers being arranged in frontfofrelatively dark wallpaper. This objective field is assumed tohave alightvalue 7."- If, however, the built-in exposure meter measures thel-ightvalues of'the field defined the frame r due to 'the presence ofthe bright surface h, representing, for ex-ample,'a windowoccupyingabout Patented Jan. 29, 1963 which the rays of light enteringthe objective are as sumed to come to a point is made coincident withthe plane in which the rays of light incident upon the photoelectriccell or" the exposure meter are assumed to come to a point, the defectis not corrected and the two frames r and r indicating the respectivefields, are still off-set as best seen in FIG. 2.

In order to avoid these disadvantages, the present invention provides anarrangement wherein the light responsive component of the exposure meteris mounted in the camera for swinging about an axis fixed relative tothe camera, and in accordance with the sharp focusing of the cameraobjective. While, as stated, the type of light responsive component isimmaterial, the camera is preferably provided with a photoelectricexposure meter. For the purpose of simplifying the disclosure of theinvention, the electrical indicator and its circuit connections with thephoto-electric cell have not been shown in all the FIG- URES of thedrawings. Also, any suitable measuring and indicating mechanism can beused and, if amplifying de vices are necessary between the photoelectriccell and the electrical indicator, these may be provided although theyhave not been shown in the drawings. For the sake of compactness, suchamplifying devices would preferably constitute transistor amplifiers.

In accordance with the present invention, the light responsive componentof the exposure meter is swung, during measurement of the light, in sucha manner that the altitude of the cone of light rays incident thereuponintersects the optical axis of the camera objective in the plane of theobject to be photographed. The objective and the photo cell have solidangles of incident light which are equal and whose vertices lie in thesame plane.

The electrical indicator component of the exposure eter can be arrangedin any desired manner upon or within the camera casing, and the lightresponsive component of the exposure meter can be arranged on or in thefront Wall of the camera. It has been found to be desirable so toarrange the swingable light responsive component in a manner such thatits point of symmetry, which is decisive for the incidence of light, islocated on a straight line extending parallel to a pair of limitinglines of the image field, which latter is assumed to be rectangular, andfurther extends at approximately the level of the axis of the cameraobjective.

In further accordance with the invention, manual adjustrnent of thephotocell to obtain the above results can be eliminated by coupling thephotocell with the sharp focusing means of the camera objective. As aresult, by operation of such sharp focusing means, both the cameraobjective and the exposure meter will be set automatically to the samepicture-taking distance, and will be centered on the same object plane.An arrangement of this type is illustrated in FIG. 4 of my saidcopending application Serial No. 616,247, now US. Patent No. 3,007,381,and forms the subject matter of such patent.

The aforementioned features represent essential features of theinvention, and it should be noted that the suggested solid or includedangle of incident light for the photocell provides sufiicient light tothe photocell for developing output currents sufficiently large forproper indication without the use of amplification, even if the includedangle is similar to the incident light angle of the camera objective.Consequently, the principles of the present invention can be applied toany camera without the necessity of additional expenditure, and willresult in a noticeable improvement in the performance of the camera.

While, by using the above-described improvements, defective lightmeasurements can be eliminated in many cases, in some cases occurring inpractice these improvements still do not provide an entirelysatisfactory measurement of the light for reasons which will now beexplained.

Normally, a picture is composed of various brightness values whichdiffer from each other, and differences in brightness and contrast areessential for a successful exposure. As previously mentioned, theexposure meter indicates an average value derived from all of thebrightness values of the picture. It will be appreciated that thevarious brightness values are not necessarily of equal importance forthe picture. Thus, the foreground may be of more interest to thephotographer than is the background, and a near group of trees maybe ofmore interest than a distant forest or vice versa. For example, if apicture of a person is to be taken from a short distance, and possiblyeven against the light, as against a bright summer sky as thebackground, the exposure of the negative material, if based on theindication of the exposure meter, will result in under exposure withrespect to the person. The picture will not be satisfactory because itsmain subject, which is the person, will appear unnaturaly dark or evenas a silhouette. A defective picture is similarly obtained in theopposite case, wherein over exposure of the most important part of thepicture is obtained if the picture of a bright object is taken againstan extensive dark background and in accordance with the indication ofthe exposure meter.

In view of the practical experience that, in using the conventionalmethod of measuring the illumination or light with conventionalcommercial exposure meters, too large an image angle is included, it hasbeen suggested to provide a light-incidence angle relative to thephotocell of only about one-tenth the value of the light incidence angleentering through the camera objective. According to this suggestion, thelight incidence angle of the photocell should be smaller than theaverage photographic objective. The reduction in output current of thephotocell, caused by the reduction of light due to the decrease in thelight incidence angle, can be compensated by electrical amplification,for example. However, this suggestion does not satisfactorily solve theproblem of always providing a correct measurement of light. It is truethat the built-in photocell of the camera, and which, in accordance withsuch suggestion, has a small light incidence angle, will measure lightoriginating from some part of the object to be photographed. However,there is no guarantee that the incident light to be measured will alwaysoriginate from the selected main part of the object whose picture is tobe taken.

The difiiculty in obtaining correct measurement of the light by means ofphotocells having small incident light angles is solved by the presentinvention in a simple and reliable manner, utilizing a pivoting orswinging mounting for the photocell. The swingable or pivotal mountingsfor photocells having a small angle of incident light are, in principle,the same as in the case of photocells having a large angle of incidentlight, and particularly photocells having a solid angle of incidentlight which is substantially equal to that of the picture-takingobjective.

Referring to FIG. 3, a camera objective 0, having an image angle oz, anda photocell p, having an incident light solid angle 18, are arranged ina common plane b including the vertices of the image angle and theincident light angle. If the objective 0 is sharply focused to theobject plane e and if, for example, the most important part of thepicture is in the center of this object plane, the photocell p should beadjusted in such a manner that the altitude of its incident light coneor pyramid intersects the optical axis of objective 0, in object plane eIf this adjustment is made, the exposure meter will measure only thelight originating from the picture portion s which may be assumed tocover from one-tenth to one-twentieth of the surface intersected, in theobject plane e by the image angle a, which is a solid angle. By soadjusting photocell p to the relatively small important portion of theobject, in most cases a correct light measurement can naturally beexpected, because this important portion of the object will almostalways coincide with the area of plane e intercepted by the light coneangle 18 of the photocell. light, such as would originate from a brightmarginal por- Thus, no side 5. tion or from a luminous sky, is presentto, affect the light measurement.

If the object plane is displaced from 2 to 2 after the photocell isre-adjusted as above, the incident light angle ,8 thereof will intersectthe'plane 2 over an area indicated by the portion .9 The surface area ofportion s has the same. ratio to thearea. of plane e intersected by theangle [3. as does the area, s to the portion of plane e intersected bythe angled. It is thus not essential that the most importantpart oftheobject be located in the middle of the Object plane, andthe mostimportant part of the picture may just as well be located in any othersection of the objectplane. A correct light measurement, for properexposure, will always result if the area of the object plane interceptedby. the solid angle ,8 coincides with such most important part of thepicture.

Theaforernentioned adjustment of the photo-cell p can be carriedout mosteffectively in the described manner when the camera is provided with ameasuring finder. In suchacase, the photocellhaving a small solid angleof .incident light is coupled for movement with the movable element ofthe measuring finder. Such an arrangement forms, the. subject matter ofmy copending application Serial No. 135,600. filed September 1, 196which is a division. of my said copending application Serial No.616,247, filed October 16, 1956, and now [1.8. Patent No. 3,007,381,issued November 7, 1961. Such a solutionis completely satisfactory inpractice in most cases. However, in certain cases, as in motion picturephotography. anddelephotography, it is desirable that the lightincidenton the photocell havea still smaller solid angle, or that lightmeasurements be taken from points outside thefield of. the measuringfinder. Accordingly, in the presentinvention, an element forming alarger image surface is mounted for pivotal movement in the camera, anda relatively small photocell is arranged for scanning discrete areasofthe image surface to measure the light fluxof the individual portions.of the object.

Referring to FIGS. and-6, a lens or lens system 46 forms an image of theobjective field included by the image angleof objective 1v on atransparent ortranslucent image surfacedl. This surface 41, which may bea ground glass. plate, is mounted in a frame 47. A photocell 34 ismounted behind the image surface 41 with its light sensitive layerdirected toward thissurface, photocell 34- being so mounted that it canbeshifted to any desired portion;

of thesurface 41.

In the arrangement shown in FIGS. 5 and 6, such-shifting isetiected byaslide 35 having guide wings 37 and 33 engated with the frame 47 so thatslide 35 is displaceablc horizontally relative to .frame 47. Between theWings 37 and38, slide 35 is formed with an elongated slot 36 in whichphotocell 34 is guided for vertical displacement. Displacementofphotocell 34 is effected through movement of. its handle33.

Frame 47.-is provided with pivot pins 52 and 53 disposed in bearings 54and 55, respectively, which are fixedly mounted in the camera, and has aZ shaped arm ts extendingrearwardly therefrom, a pin 49 being insertedin the free end of arm48. Pin 49 is engated in thefork 50 ofadouble-armed lever 51 having a pivot-pin $6 intermediate its, endsengatedin-bearings 57 and 53 fixed in the camera, The opposite or lowerend of the lever 51 is formedwith asecond fork 5% in which is engated apin 45 fixedly mounted ona-displaceable part of the objectivemountl. Inthe position shown in FIGS. 5 and 6, the objective-1 and the exposuremeter frame 4-7 are adte t d o n in t Tghe arrangementofFIGS. 5 and6operates as follows. If objectiveLis. sharply focused, as byaxialdisplacement along its. optical-axis, to an object located at afinite distame, the. elements 45, 51, -49, and 48 effect a simultaneousswinging offrame 47 in such a manner that the surface 41 and the opticalmeans .46 arranged in front of this surface, together with the photocell34 located behind the image surfge, are directed toward the same surfacein the object plane to which the objective 1 is sharply focused. If theuser has selected the mostimportant part of the picture to be taken, hecan move the handle 33 to shift the photocell 3 3- to the correspondingportion of the surface 41 and thus measure the light flux of theselected portion of the picture to be taken.

The image formed on the image surface 41 need not-be sharp and need noteven be observed by the photographer. As sharpness of the image is notimportant, nospecial lenses need to be used for the lens system 46 andthis system will not even need to be arranged for sharp focusing,

thus making the cost of manufacture of such devices very inexpensive.Preferably, an arrangementsuch as shown in FIG. 4 is used, in which theimage appearingin the viewfinder is utilized for scanning the image ofthe surface 47.

Referring to FIG. 4, the viewfinder screen is indicated at 30 as dividedinto a grid. A rod -32 is secured to the photocell 34, or preferably tothe handle 33 thereof, and extendsvertically upwardly therefrom and thenlaterally into a position behind .the viewfinder screen 30. Aimark 31 isprovided on the free end of the rod 32, and the arrangement of vtheparts is so selected that the particular portion of screen 30 which hasthe mark 31.positioned thereover will correspond exactly totheparticular portion of screen 41which is then aligned with thephotocell 34. Thus, by observing the, viewfinder screen 30, thephotographer may manipulate the handle 33 of the photocell 34 to scanany desired area of the image seen in the viewfinder and thus alsoappearing on the image surface 4-1. v movable on the guides 39 and 4%which maybe upper and lower edges of the frame 47 of FIGS. 5 and 6. Therelatively small amount of angular tilting of the frame 47 will not inany manner adversely affect the position of the mark 31 with respect tothe viewfinder screen 30.

A modification of this arrangement is shown in lFIG. 7.

In this modification,

spondingly numbered grid arrangement is provided on the screen scannedby the photocell operable by the handle 33. A fork shaped guide means 66is provided forfthethat then having the mark 31 positioned'thereover.For

example, in FIG. 7, the mark 31 is positioned over the square 6 and thephotocell operated by the handle 33 is positioned over thesquare 6 ofits associated screen.

A preferred embodiment of the invention, characterized by simplicity ofoperation, is illustrated diagrammatically in perspective in FIG. 8.With this device, all that is necessary, in order to effect measurementof the light fiux of the mostimportant element of the picture, is tooperate the manual knob 13 while observing the image in the viewfinder.The objective mount 1 is positioned on a front plate 2a of the camera,and plate 2:: also carries the window 61 of the viewfinder. The filmexposure aperture or window 161) is aligned behind the objective mount1, and a light shaft or passage 62 extends from the window 61 to theeyepiece of the viewfinder (not shown).

A front optical element or means 64 projects through a recess 63 in theplate 2a, and condenses and focuses lightrays incident on the-photocell65. The solid angle of the focused light rays should be small and shouldin- The slide 35' is illustrated as horizontally the squaresformed bythe grid marks on the viewfinder screen 39 arenumbered, and acorretersect, in the object plane, the most important portion of thepicture to be taken. Conductors 161 and 1692 supply the output currentof the photocell 65 to a measuring mechanism or electrical indicatorlocated in casing 103, and whose indication is visible through a windowW4. Means other than the particular optical means 64 illustrated may beused for condensing and focusing the light incident on the photocell 65.

Photocell 65 is secured to one end of a rod 66 which passes through aball 67 intermediate its ends and has a ball 68 on its other end. Ball63 is engaged in a ball socket 69 and is pressed thereagainst, as by aspring housed in the rod 66 which may be made of a tubular telescopingdesign. Socket 6 is secured to the upper end of a rod 71 carrying, justbelow the socket 69, a ballbearing 7d, the lower end of the rod 71 beingsecured to a plate having an opening 72 therethrough. The ball 67 has abearing support in supports 73 and 74, and the ballbearing 7t) has abearing support in the support 75, the supports 73, '74 and '75 beingmounted on a hinge leaf 77 pivoted about a shaft 76 which is fixedlymounted in the camera as illustrated. A rod 79 has one end secured tohinge leaf 77, as at 73, the fastening 73 providing an articulatedattachment for the rod 79, and the other end of the rod '79 being joinedto the objective mount 1 as indicated at fill. The pull rod 79, actingthrough the hinge leaf 77, adjusts the photocell 65 in accordance withthe displacement of the objective 1 so that the photocell light conealtitude intersects the optical axis of the objective 1 in theparticular object plane to which the objective 1 is sharply focused.

Scanning of the photocell 65 so that it will measure the light from themost important part of the object plane is effected by the handle 33which is rigidly connected by a rod 33 with an angle member 82 withinthe camera. Rod 83 can be displaced along a slot 84 in the camera cover2b, as well as being displaceable inwardly and outwardly relative to thecamera cover 212. The angle member 82 is guided by the parallel rodsystem 35, 86, 87, 88 so that it is movable substantially only parallelto the wall 2a of the camera. The plane of movement of the angle member82 is so designed that it corresponds to the plane of the viewfinderimage. A guiding bracket 39 is provided to further assure proper guidingof the angle member $2 by its parallel rod system, guide bracket d9being fixedly mounted in the camera.

An angled connecting rod d1 is connected to the angle member 92 andcarries, at its free end, the mark 31 cooperable with the finder imageviewed in the window 61. A rod or is also rigidly secured to the bracket82 and its free end has an articulated connection in the aperture in theplate 72. It will be observed that, by operating handle 33, the mark 31can be positioned at any desired portion of the viewfinder image asviewed in the window 61, and that simultaneously the photocell 65 andits light condensing and focusing element 64- are adjusted to thecorresponding portion of the area of the object plane intercepted by theimage angle of the objective 1.

The proper motion of the photocell essential for correct measurement ofthe light fiux can be attained by proper selection of the length of thelever rods 71 and 66, which rods are universally mounted. Preferably,suitable adjusting means are arranged either on the lever system or onthe hinge leaf 77. Adjustment of the an lar movement of the photocellcan be simply effected by constructing the plate 72 for adjustmentrelative to the rod 71 and for clamping of the plate 72 in its adjustedposition.

While the embodiments of the present invention can be used in all typesof cameras, they offer particular advantages when used in cameraprovided with fully automatic operation under the control of theexposure meter, so that adjustment'of exposure factors, such asdiaphragm aperture and shutter time, is automatically effected.

While specific embodiments of the invention have been shown anddescribed indetail to illustrate the applica-" tion of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

. 1. In a photographic camera, an objective including componentsrelatively axially adjustable for focusing of the objective; a photocellarranged to have light incident thereupon through a solid angle which isa minor fraction of the image angle of said objective; an optical systemarranged to direct light from the objective field upon said photocellalong a ray path independent of the ray path entering said objective;means mounting said optical system and photocell for angular adjustmentof the optical axis of said optical system relative to the optical axisof said objective; coupling means interconnecting an axially adjustablecomponent of said objective and said optical system, and effective toangularly adjust said optical system and photocell in accordance withthe focusing of the objective so that the axes of the objective and ofsaid optical system intersect substantially in the plane of the sharplyfocused field of said objective; and means mounting said photocell formovement relative to said sharply focused objective field to scan thelight values of discrete areas of the latter.

2. In a photographic camera, as claimed in claim 1, a viewfinder havingmeans providinga field of view corresponding substantiaily to the imageangle of the objective; and an indicator element coupled to saidphotocell for movement therewith, said indicator element including anindicator mark extending into the field of view of said viewfinder; theposition of said indicator mark in the field of view of the viewfindercorresponding, in any position of said photocell, to the discrete areaof said sharply focused objective field then being scanned by saidphotocell; whereby an observer, looking into the viewfinder, may movesaid photocell to scan the light value of any discrete area of the fieldof view of the viewfinder.

3. In a photographic camera, an objective including componentsrelatively adjustable axially for focusing of the objective; atranslucent screen; an optical system providing an image of theobjective field, as included in the image angle of the objective, onsaid translucent screen, and along a ray path independent of thatentering said objective; at photocell mounted for movement over saidscreen for scanning discrete areas thereof, the incident light angle ofsaid photocell being a minor fraction of the image angle of saidobjective; means mounting said optical system for angular adjusting ofits optical axis relative to the optical axis of the objective; andcoupling means interconnecting an axially adjustable component of saidobjective and said optical system and effective to angularly adjust saidoptical system in accordance with the focusing of the objective so thatthe axes of the objective and of said optical system intersectsubstantially in the plane of the sharply focused field of saidobjective; whereby said photocell may be moved to scan the light valuesof discrete areas of said sharply focused field as imaged in saidtranslucent screen.

4. In a photographic camera as claimed in claim 3, a viewfinder havingmeans providing a field of view corresponding substantially to the imageangle of the objective; an indicator element coupled to said photocellfor movement therewith and including an indicator mark positioned in thefield of view of said viewfinder; the position of said indicator mark inthe field of view of said viewfinder corresponding, in any position ofsaid photo-- cell, to the discrete area of said sharply focused fieldthen being scanned by said photocell; whereby the observer, looking intothe field of view of said viewfinder, may position said photocell toscan the light value of any discrete area of the sharply focused fieldof the objective.

5. In a photographic camera, an objective including componentsrelatively adjustable axially for focusing of the objective; aviewfinder having means providing a field of view correspondingsubstantially to the image angle of the objective; a photocell arrangedto have light incident there-upon through a solid angle which is a minorfraction of the image angle of said objective; an optical systernarranged to direct light from the objective field upon said photocell;means mounting said photocell for movement relative to said sharplyfocused objective field to scan the light values of discrete areas ofthe latter; and an indicator element coupled to said photocell formovement therewith and including an indicator mark positioned in thefield of view of said viewfinder, the position of said indicator mark inthe field of view of said viewfinder corresponding, in any position ofsaid photocell, to the discrete area of said sharply focused objectivefield then being scanned by said photocell; whereby an observer,loo-king into the field of view of said viewfinder, may move saidphotocell to measure the light value of any selected discrete area ofsaid sharply focused objective field.

6. In a photographic camera, an objective including componentsrelatively axially adjustable for focusing of the objective; aviewfinder having means providing a field of view correspondingsubstantially to the image angle of the objective; a translucent screen;an optical system providing an image of the objective field, as includedin the image angle of the objective, on said translucent screen; aphotocell mounted for movement over said screen for scanning discreteareas thereof, the incident light angle of said photocell being a minorfraction of the image angle of said objective; and an indicator elementcoupled to said photocell for movement thereof and including anindicator mark positioned'in the field of view of said viewfinder, theposition of said indicator mark in the field of View of said viewfindercorresponding, in any position of said photocell, to the discrete areaof said screen then being scanned by said photocell; whereby anobserver, looking into the field of view of said viewfinder, may movesaid photocell to scan any selected discrete area of the sharply focusedobjective field as to light value.

7. In a photographic viewfinder, as claimed in claim 6, said translucentscreen being substantially rectangular and corresponding, in area anddimensions, to the field of view of said viewfinder; a slide extendingacross said screen parallel to one pair of sides of the latter, andmounted for movement in a direction parallel to the other pair of sidesof said screen; said slide being longitudinally slotted, and saidphotocell being adjustable along the slot in said slide whereby, duringits scanning movement, said photocell may be moved parallel to eitherside of said screen for positioning over any part of the total area ofsaid screen.

8. In a photographic camera, as claimed in claim 6, said translucentscreen being rectangular and corresponding in area and dimensions to thefield of view of said viewfinder; said translucent screen and the fieldof view of said viewfinder being divided into an equal number ofdiscrete areas arranged in columns and rows respectively parallel toadjacent sides of said screen; a guide providing a first track extendingthrough one column of said areas of said screen, and branch tracksintersecting said first track, each extending longitudinally of adifferent row of said areas; said photocell being mounted for movementalong any of said tracks whereby any of the discrete areas of saidscreen may be scanned by said photocell.

9. A photographic viewfinder, as claimed in claim 3, in which saidscreen is mounted in a rectangular frame supporting said optical system;and means pivotally mounting said frame in said camera for pivotalmovement about an axis perpendicular to an axial plane through saidobjective; said coupling means comprising pivotally interconnectedlinkage interconnecting said frame and said last-mentioned axiallyadjustable component of said objective.

10. A photographic viewfinder, as claimed in claim 8, including a pairof rails extending along opposite sides of said frame; a slide mountedfor movement along said rails and extending across said frame, saidslide being formed with a slot extending longitudinally thereof, saidphotocell being adjustable along the slot of said slide for scanning anyselected discrete area of said screen.

11. In a photographic viewfinder, as claimed in claim 1, a supporthingedly mounted in said camera for swinging movement in a directionperpendicular to an axial plane of said objective; said coupling meansinterconnecting said support and said last-mentioned axially adjustablecomponent of the objective; said optical system and said photocellforming a unit mounted on said support for movement therewith; meansmounting said unit on said support for universal movement relative tothe field of the objective in any position of said support; a viewfindermounted in said camera and having means providing a field of viewcorresponding substantially to the image angle of the objective; anindicator element extending substantially parallel to the plane of thefield of view of the viewfinder and having an indicator mark movableover said field of view; manually operable means connected to saidindicator element for scanning said mark with respect to the field or"view of said viewfinder; and linkage interconnecting said indicatorelement to said unit, and including said universal mounting of saidunit, efiective to adjust said unit to scan the particular area of thefield of view of said objective corresponding to the area of the fieldof view of said viewfinder then being scanned by said indicator mark;whereby an observer, looking into the field of view of said viewfinder,may, through said manual means, operate said unit so that said photocellmeasures the light value of the discrete area of the field of view ofthe objective corresponding to the discrete area of the field of View ofsaid viewfinder then having said indicator mark aligned therewith.

12. In a photographic camera as claimed in claim 11, parallel linkageinterconnecting said indicator element and said manual operating meansto said unit, whereby said indicator element is moved parallel to theplane of the field of view of said viewfinder during universaladjustment movement of said unit.

References Cited in the file of this patent UNITED STATES PATENTS2,796,799 Strauss June 25, 1957 2,990,757 Ponsar July 14, 1961 FOREIGNPATENTS 746,837 Great Britain Mar. 21, '1956

1. IN A PHOTOGRAPHIC CAMERA, AN OBJECTIVE INCLUDING COMPONENTSRELATIVELY AXIALLY ADJUSTABLE FOR FOCUSING OF THE OBJECTIVE; A PHOTOCELLARRANGED TO HAVE LIGHT INCIDENT THEREUPON THROUGH A SOLID ANGLE WHICH ISA MINOR FRACTION OF THE IMAGE ANGLE OF SAID OBJECTIVE; AN OPTICAL SYSTEMARRANGED TO DIRECT LIGHT FROM THE OBJECTIVE FIELD UPON SAID PHOTOCELLALONG A RAY PATH INDEPENDENT OF THE RAY PATH ENTERING SAID OBJECTIVE;MEANS MOUNTING SAID OPTICAL SYSTEM AND PHOTOCELL FOR ANGULAR ADJUSTMENTOF THE OPTICAL AXIS OF SAID OPTICAL SYSTEM RELATIVE TO THE OPTICAL AXISOF SAID OBJECTIVE; COUPLING MEANS INTERCONNECTING AN AXIALLY ADJUSTABLECOMPONENT OF SAID OBJECTIVE AND SAID OPTICAL SYSTEM, AND EFFECTIVE TOANGULARLY ADJUST SAID OPTICAL SYSTEM AND PHOTOCELL IN ACCORDANCE WITHTHE FOCUSING OF THE OBJECTIVE SO THAT THE AXES OF THE OBJECTIVE AND OFSAID OPTICAL SYSTEM INTERSECT SUBSTANTIALLY IN THE PLANE OF THE SHARPLYFOCUSED FIELD OF SAID OBJECTIVE; AND MEANS MOUNTING SAID PHOTOCELL FORMOVEMENT RELATIVE TO SAID SHARPLY FOCUSED OBJECTIVE FIELD TO SCAN THELIGHT VALUES OF DISCRETE AREAS OF THE LATTER.